The electrician is often called upon to work with a large number of wires, many times bundled, some of which may be live and others dead. Although usually color coded for identification, their condition, i.e. either live or dead, needs to be routinely verified before they are handled. In a typical days work perhaps hundreds of tests must be performed to determine voltage levels or to verify continuity, before and after wiring operations.
In a series of wiring operations it may be necessary to perform various tests. For example, when working with household voltages one might first test for AC voltage (or for DC voltage in certain countries), then perhaps for DC offset, to be certain that a wire is safe for handling. After the wiring operation is completed a test for continuity may be done. And after power is reapplied, then usually another test of voltage to be certain the operation is properly done. The voltages encountered can and do vary over a wide range, i.e. from zero to over six hundred volts in some situations, and thus the test instrument must not only provide AC, DC and continuity modes, but must also accommodate this wide range of voltage levels.
To be efficient in his work, an electrician needs a single instrument capable of performing the above-noted tests quickly and safely. The instrument must be easy to hold, eaasy to set, easy to read, and foolproof. Unfortunately, digital voltage testers have heretofore been lacking in one way or another, especially from a practical point of view. They either are too complicated for efficient, safe and reliable operation, absent sufficient capability to be practically useful, lacking in sufficient safeguards or self testing capability to assure reliability, or are too bulky or flimsy.
They have not, as the present invention does, coordinated the incorporated test functions to achieve the flexability and ease of operation that is really needed.